The World’s Coolest Plastic Roof? Ask Minnesota Vikings fans.

Well, if you’ve seen a Monday Night football in Minnesota game – the answer was yes.

No, ETFE wasn’t a mid-season signing by the Vikings. ETFE wasn’t out on the field, but it was all over the field – literally.

ETFE (ethylene tetrafluoroethylene) – is what makes up that see-through roof of the Vikings stadium (U.S. Bank Stadium).

If you remember a few years ago, the Vikings’ old stadium with a roof, the Metrodome, collapsed in a snowstorm. And if you’re going to a Vikings’ game in December, a roof IS nice. So when the Vikings started work on a new stadium, they turned to ETFE for the lid. Why?

ETFE is a polymer-made film with some pretty remarkable qualities:

It can be stretched out up to three times its original length (without weakening).

It lets through more light than glass, so much that you can have a grass field underneath it.

It is lightweight enough to cover a football field without massive pillars to hold it up (1/100th the weight of a glass roof).

And it is strong enough to survive a Minnesota snowstorm (it can hold up 400 times its own weight), and this roof also has a special ink built in, to reflect heat and help melt snow.

Did you know?

Ethylene tetrafluoroethylene IS a mouthful, but it comes from a simple source: ethylene. And ethylene itself is pretty basic: one of the seven “building block” chemicals that’s made by running steam through petroleum or natural gas, and breaking those big molecules down into the building blocks, like ethylene.

And while ethylene tetrafluoroethylene might not be a familiar name, there are lots of sports arenas, here and around the world, where you might see ETFE.

Other football teams play it under it, like the Atlanta Falcons. And their Mercedes Benz Stadium is also home to the “other” football, soccer – so you’ll find Atlanta United FC there too. In fact, maybe there is something special between football (both kinds) and ETFE. Los Angeles FC’s new Banc of California Stadium features ETFE. The dominant club in German soccer, Bayern Munich packs 75,000 supporters under the ETFE in its Allianz Arena.

And if you were in Mexico, to take in a Puebla FC match, yep, you’d find Estadio Cuauhtémoc Stadium sporting ETFE.

But there’s another cool feature about ETFE, and you can see it in that picture of Allianz Arena. For a big space, it’s used in layers (3, for example, in Minnesota), and while it’s clear during the day, at night that space between the layers allows for light transmission and a light show. Like at Allianz, or like the Water Cube (which you might know from the 2008 Summer Olympics)…

Oh, and that combination of strength and lightweight makes some other special effects possible too – like opening and closing the roof of Atlanta’s Mercedes-Benz Stadium. Take a look at these 200-foot ETFE “flower petals” in motion…

…and next time you’re out for a game (or a match), look up. If there’s a roof, and you can see through it, “your house” might be an ETFE house.

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